Fiction, no matter how unpalatable, should never be a crime.
The Act created the somewhat misleadingly titled offence of Possession of Prohibited Images of Children.
The offence is misleadingly titled as unlike the offence under the Protection of Children Act 1978, Possession of an Indecent Photograph of Children (and Pseudo-photographs), Section 62 does not require a child, indeed it does not require a human being at all, the offence covers imaginary "children" (being characters under the age of 18 or appearing to be so) , imaginary "persons" and for good measure, "imaginary animals".
While the Protection of Children Act 1978 rightly sought to punish those who make and possess images of the sexual abuse of children, the Coroners and Justice Act 2009 seeks to punish expression, it specifically criminalises that which is nothing more than the imagination set down on paper, canvas or bytes.
In board terms it is fundemantally important the the limits on individual freedom in a free society are set where an identifiable harm is occassioned or likely to be occassioned, this law does not do that.